The present invention relates to a surgical cutting instrument, and more particularly, to a surgical cutting instrument capable of, while being inserted into a body cavity, particularly a joint cavity of the knee, for example, performing a easy and reliable cutting and evacuating operation of a cartilage, bone, fibrous tissue, tumor or the like.
A conventional operation of a joint generally employs an incision method (open surgery). By way of example, a commonly used operation of the knee such as to remove a tumor on the patella or to excise a damaged cartilage or a bone from the knee joint requires a large incision of an epithelium. Consequently, the operation is attended with a trauma by the incision. Thus, the trauma will cause pain and limitations of movement. Furthermore, a considerable time is required for recovery from the trauma.
Accordingly, there has recently been proposed an instrument in which under observation with an arthroscope (endoscope) a small perforation is provided on an epithelium without incising the knee epithelium and an operation is effected inserting a probe into the perforation (closed surgery). For instance, such instruments are disclosed in U.S. Pat. No. 4,203,444 and U.S. Pat. No. 4,246,902.
The prior art instrument disclosed in U.S. Pat. No. 4,203,444 comprises an elongate external stationary tube defining a side-facing, axially extending shaving port on the periphery of the external tube, an internal tube which is rotatably mounted within the external tube and defines an internal, rotary blade at the shaving port, a suction apparatus and a drive motor. The instrument severs tissue or the like by rotating the rotary blade with the drive motor and draws shavings by suction to remove them through the internal member.
With the conventional instrument of the above construction, since in the shaving port, an outer cutting edge is formed on the inner periphery of the external tube and the rotary blade forms an inner cutting edge, it is difficult to take steady aim at a tissue to be cut and a bite between the outer and the inner cutting edges is not good. In addition, since the cutting operation is effected only after a tissue to be cut is drawn in the shaving port of the external tube by means of the suction apparatus, it is difficult to cut a tissue such as a cartilage or a bone. To rotate the internal tube forming a suction channel therein, a rotary shaft passes through the suction channel and therefore cut or shaved tissue is not smoothly sucked and withdrawn.
The prior art instrument disclosed in U.S. Pat. No. 4,246,902 comprises a probe-like outer, elongate member having a distal end with a cutting aperture in a side wall thereof, an inner cutting member which is slidably disposed within the outer member and has a distal end defining a cutting edge positioned at said distal end of the outer member, a suction apparatus and a drive mechanism for the inner cutting member. The instrument cuts a tissue to be cut which is drawn by suction in the cutting aperture by reciprocation of the inner cutting member and then the cut tissue is sucked and evacuated. The instrument thus constructed, however, has disadvantages as indicated in the former prior art, also. Specifically, since the inner cutting member which is disposed within the outer member forms an inner cutting edge, it is difficult to take steady aim at a tissue to be cut and a bite between the outer member and the inner cutting edge is not good. In addition, it is difficult to cut a comparatively hard tissue such as a cartilage or bone. Since the inner cutting member is slidably disposed within a suction channel passage, cut tissue is not smoothly sucked and withdrawn.